A major change in telecommunication industry is Voice over Internet Protocol (VoIP). VoIP offers interactive communications. It differs from conventional circuit switched networks. It allows people to communicate with each other at very low rates. The transmission of real time voice data is not as easy as ordinary text data. The real time voice transmission faces lot of difficulties. It suffers from packet loss, delay, security and quality. These factors will affect the communication, degrades the performance and quality of a VoIP. This paper addresses the security aspects of VoIP to improve the quality.